Conventional powertrain mounts exist in many varieties and generally operate to provide engine isolation while concurrently controlling engine motion. The typical hydraulic mount includes a pumping chamber surrounded by relatively thick elastomeric walls with an orifice track opening to the chamber and extending to a reservoir that is typically surrounded by a highly flexible rubber diaphragm. The reservoir is typically located on the opposite side of a partition from the pumping chamber. During compression operation, fluid is pressurized in the pumping chamber and is caused to flow through the orifice track to the reservoir. During rebound operation, fluid is drawn back to the pumping chamber from the reservoir by operation of the pumping chamber. The geometry of the pumping chamber, orifice track and reservoir are tuned so that the fluid in the orifice track resonates at certain frequencies. This is used to provide a peak damping effect at a selected frequency to reduce vehicle harshness from road induced vibrations.
Hydraulic mounts have been in widespread use for some time and their operation is desirable in many applications. Accordingly, new variations for use in additional applications and variations that provide advantages are continuously being sought. One of the essential characteristics of a mount design is that it is durable over an extended life in a severe application environment where high loads are imposed on the mount, developing high internal pressures and high stresses. Therefore, the construction of the hydraulic mount is important. A sufficiently durable mount must perform the functions of locating and supporting the weight of the vehicle's engine while providing adequate isolation. The static load on the mount must be supported for long periods. Static loads place stresses on the bonding between rubber and metal components, and may cause a mount to sag after extended periods. Accordingly, durability improvements are advantageous.